The list is nice, but ONLY 4-6 CSR (V or Vmax) in 1 case (20 Box).
And seems there's just 1-2 CHR & CSR per box, if this Japanese set had around 100 secret rare. You may not be able to collect all of them even you open 10 case... The price will be crazy.
You're right. As long as it's power is once per turn, there's not much threat to create. Of course this card can be a savior drawing the one and only one key card, but since this is once per turn, this will not be a tough one to encounter.
I think it will not be that easy.
The biggest issue is you can have only 1 card for each of them, and the only option to "summon" it out is all 4 pcs are in your discard pile. If you get it stuck in prize, or not enough options to discard, it will still be an issue.
Last but not least, the...
Yup I'm talking Japanese release date.
For Western release schedule, rotation should have updated.
But still, various combination can be made.
And best defense I can think of right now is the Spiritomb.
https://bulbapedia.bulbagarden.net/wiki/Spiritomb_(Peerless_Fighters_49)